Date: Sat, 15 Sep 2007 16:52:01 -0500 From: Mike Karels <karels@karels.net> To: Julian Elischer <julian@elischer.org> Cc: FreeBSD Net <freebsd-net@freebsd.org>, David Christensen <davidch@broadcom.com>, Jack Vogel <jfvogel@gmail.com> Subject: Re: BCE on FreeBSD and oversized packet acceptance. Message-ID: <200709152152.l8FLq1lq042729@redrock.karels.net> In-Reply-To: Your message of Sat, 15 Sep 2007 12:30:19 -0700. <46EC32CB.2030202@elischer.org>
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> Mike Karels wrote: > >>> Secure Computing (my employer) has a modification that seems reasonable > >>> to me (well, I guess I wouldn't have done it otherwise). We adopted the > >>> existing but unused JUMBO_MTU capability flag, and, if enabled, instructs > >>> the driver to receive jumbo frames according to the hardware limits. With > >>> that flag, the MTU may be 1500, but the driver is still instructed to > >>> receive jumbo frames even without sending them. The reason for this > >>> is the lack of a way to negotiate the use of jumbo frames per host > >>> (as far as I know; such a thing would certainly be useful, though). > > > >> certainly the adoption of that flag is reasonable. > >> is it settable from ifconfig? > >> it's probably better than saying "enable jumbo reception > >> if mtu is greater than 1600 bytes" or whatever.. > > > > Yes, the flag is settable with ifconfig. It expands the "accept > > what is convenient" to "and also accept whatever is reasonable > > for jumbo" (for this NIC). > > > > Mike > It would be interesting to get patches to look at.... > Does it require changing all the drivers? > I assume that if so, you'd only patch those you are interested in. I can provide diffs if they are of interest. As you say, this is driver-by-driver. We have done only em at this point, as we don't support 9K clusters. (Long story, has to do with resource management.) Mike
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